Micromachine and method of manufacturing the micromachine

ABSTRACT

To obtain a micromachine for use as a high frequency filter having a high Q value and a higher frequency band. 
     In a micromachine ( 20 ) including: an input electrode ( 7   b ), an output electrode ( 7   a ), and a support electrode ( 7   c ) disposed on a substrate ( 4 ); and a band-shaped vibrator electrode ( 15 ) formed by laying a beam (vibrating part) ( 16 ) over the output electrode ( 7   a ) with a space part (A) interposed between the output electrode ( 7   a ) and the vibrator electrode ( 15 ) in a state in which both end parts of the vibrator electrode ( 15 ) are supported on the input electrode ( 7   b ) and the substrate ( 4 ) with the support electrode ( 7   c ) interposed between the substrate ( 4 ) and the vibrator electrode ( 15 ), the entire surface of both end parts of the vibrator electrode ( 15 ) from an edge of the end parts to the beam ( 16 ) is completely fixed to the input electrode ( 7   b ) and the support electrode ( 7   c ).

RELATED APPLICATION DATA

This application claims priority to PCT/JP03/08905, filed Jul. 14, 2003,and Japanese Application No. P2002-22 1433, filed Jul. 30, 2002.

The present invention relates to a micromachine and a method ofmanufacturing the same, and particularly to a micromachine in which avibrator electrode is disposed so as to cross over an output electrodewith a space part interposed between the output electrode and thevibrator electrode, and a method of manufacturing the same.

With progress of technology for microfabrication on a substrate,micromachine technology is drawing attention which forms amicrostructure, and an electrode, a semiconductor circuit and the likefor controlling driving of the microstructure on a substrate such as asilicon substrate, a glass substrate or the like.

One of micromachines is a micro-vibrator proposed for use as a highfrequency filter in radio communication. As shown in FIG. 11, amicro-vibrator 100 is formed by disposing a vibrator electrode 103 overan output electrode 102 a disposed on a substrate 101 with a space partA interposed between the output electrode 102 a and the vibratorelectrode 103. The vibrator electrode 103 has one end part connected toan input electrode 102 b formed by the same conductive layer as theoutput electrode 102 a. When a voltage of a specific frequency isapplied to the input electrode 102 b, a beam (vibrating part) 103 a ofthe vibrator electrode 103 disposed over the output electrode 102 a withthe space part A interposed between the output electrode 102 a and thevibrator electrode 103 vibrates, thus a capacitance of a capacitorformed by the space part A between the output electrode 102 a and thebeam (vibrating part) 103 a is changed, and this is output from theoutput electrode 102 a. A high frequency filter including the thusformed micro-vibrator 100 can achieve a higher Q value than highfrequency filters using surface acoustic waves (SAW) and thin filmelastic waves (FBAR).

Such a micro-vibrator is manufactured as follows. First, as shown inFIG. 12A, an output electrode 102 a, an input electrode 102 b, and asupport electrode 102 c made of polysilicon are formed on a substrate101 whose surface is covered with an insulating layer. These electrodes102 a to 102 c are formed such that the input electrode 102 b and thesupport electrode 102 c are disposed on both sides of the outputelectrode 102 a. Next, a sacrificial layer 105 made of silicon oxide isformed over the substrate 101 in a state of covering the electrodes 102a to 102 c.

Next, as shown in FIG. 12B, connecting holes 105 b and 105 c reachingthe input electrode 102 b and the support electrode 102 c are formed inthe sacrificial layer 105. Thereafter a polysilicon layer 106 is formedon the sacrificial layer 105 including the inside of the connectingholes 105 b and 105 c.

Next, as shown in FIG. 12C, a band-shaped vibrator electrode 103crossing over the output electrode 102 a is formed by pattern etching ofthe polysilicon layer 106. At this time, in order to prevent etching ofthe input electrode 102 b and the support electrode 102 c made ofpolysilicon, the pattern etching of the polysilicon layer 106 isperformed such that the connecting holes 105 b and 105 c are coveredcompletely.

Thereafter the sacrificial layer 105 is selectively removed to therebyform a space part A between the output electrode 102 a and the vibratorelectrode 103 as shown in FIG. 11. Thus the micro-vibrator 100 iscompleted.

However, in the thus obtained micro-vibrator 100, an eaves part B notfixed to the input electrode 102 b or the support electrode 102 c isformed at an edge part of an anchor (supporting part) 103 b at both endsof a beam 103 a. Such an eaves part B greatly affects vibration of thebeam 103 a when the vibrator electrode 103 is further reduced.

FIG. 13 is a diagram showing a relation between length L of the beam ofthe micro-vibrator 100 having the above-described structure and naturalfrequency of vibration. As shown in this figure, a theoretical naturalfrequency of vibration (Theory) based on the following Equation (1) isproportional to (1/L²).

$\begin{matrix}{f_{R} = {\frac{0.162h}{L^{2}}\sqrt{\frac{EK}{\rho}}}} & (1)\end{matrix}$

-   -   h: film thickness    -   E: Young's modulus    -   K: electromagnetic coupling factor    -   ρ: film density

However, in the micro-vibrator 100 having the above-described structure,as is clear from a result of simulation using a finite element method,it is difficult to increase the natural frequency of vibration inproportion to (1/L²) due to effects of the eaves part B in a range (100MHz and higher) where the beam length L is reduced to less than 10 μmand the beam 103 a and the anchor 103 b supporting the beam 103 a are ofsubstantially the same length.

It is accordingly an object of the present invention to provide amicromachine having a vibrator electrode capable of realizing highernatural frequency of vibration in proportion to (1/L²) even in a highfrequency range of 100 MHz and higher.

SUMMARY OF THE INVENTION

In order to achieve the object, according to the present invention,there is provided a micromachine characterized by including: an inputelectrode and an output electrode disposed on a substrate; and aband-shaped vibrator electrode formed by laying a vibrating part overthe output electrode with a space part interposed between the outputelectrode and the vibrator electrode in a state in which both end partsof the vibrator electrode are supported on the input electrode and thesubstrate; wherein an entire surface of each of the end parts of thevibrator electrode from an edge of each of the end parts to thevibrating part is completely fixed to the input electrode and thesubstrate.

In the thus included micromachine, since the entire surface of both endparts of the vibrator electrode from the edge of the end parts to thevibrating part is completely fixed to the base, only the vibrating partis disposed with a space part interposed between the vibrating part andthe base. Therefore, when the vibrator electrode is vibrated by applyinga voltage of a predetermined frequency to the vibrator electrode via theinput electrode, only the vibrating part is involved in vibration, andvibrates. Thus, a natural frequency of the vibration is closer to thetheoretical value (a value inversely proportional to a square of lengthL of the vibrating part), making it easy to achieve higher frequency bymicrofabrication.

The present invention also represents a method of manufacturing the thusincluded micromachine, which method is carried out by the followingprocedure.

In a first manufacturing method, an input electrode and an outputelectrode are formed by patterning a first conductive layer on asubstrate, and then an insulative protective film is formed on an uppersurface of the input electrode and on the substrate on an opposite sidefrom the input electrode with the output electrode interposed betweenthe input electrode and the opposite side. Next, a sacrificial layercapable of being etched selectively without affecting the protectivefilm is formed on the substrate in a state of covering the inputelectrode and the output electrode with a surface of the protective filmexposed. Connecting holes reaching the input electrode and the substrateare formed in the protective film. Thereafter a band-shaped vibratorelectrode having both end parts completely covering insides of theconnecting holes, an edge of each of the end parts being situated on theprotective film, and having a central part crossing over the outputelectrode is formed by forming and patterning a second conductive layeron the sacrificial layer including the insides of the connecting holes.Next, a space part is created between the vibrator electrode and theoutput electrode by selectively removing the sacrificial layer.

According to the first manufacturing method, the pattern of the vibratorelectrode is formed such that the vibrator electrode covers the insidesof the connecting holes and an edge of each of the end parts of thevibrator electrode is situated on the protective film in a state of thesacrificial layer being laid on the substrate so as to expose theprotective film having the connecting holes formed therein. Thus, onlythe central part of the vibrator electrode is disposed on thesacrificial layer in a state of the entire surface of both ends of thevibrator electrode being disposed on the connecting holes and theprotective film. Then, in this state, the sacrificial layer is removedselectively without affecting the protective film. Therefore, thevibrator electrode is formed which has a shape such that the space partis provided only under the central part and such that without the edgeof both end parts of the vibrator electrode being extended beyond thesurface of the protective film, the entire surface of both end parts ofthe vibrator electrode is fixed to the protective film and theconnecting holes. Since the pattern of the vibrator electrode is formedso as to cover the connecting holes, even when the input electrodedisposed at a bottom part of the connecting hole is formed by the samematerial as the vibrator electrode, the input electrode within theconnecting hole is not affected by the pattern formation of the vibratorelectrode.

In a second manufacturing method, an input electrode and an outputelectrode are formed by patterning a first conductive layer on asubstrate, and then a sacrificial layer covering the input electrode andthe output electrode is formed over the substrate. Next, a connectinghole reaching the input electrode and a connecting hole reaching asurface of the substrate on an opposite side from the input electrodewith the output electrode interposed between the input electrode and theopposite side are formed in the sacrificial layer, and a secondconductive layer capable of being etched selectively without affectingthe first conductive layer is formed on the sacrificial layer includingthese connecting holes. Thereafter a band-shaped vibrator electrodehaving an edge of both end parts disposed within each of the connectingholes, and having a central part crossing over the output electrode isformed by selective pattern etching of the second conductive layerwithout affecting the first conductive layer. Next, a space part iscreated between the vibrator electrode and the output electrode byselectively removing the sacrificial layer.

According to the second manufacturing method, the pattern of thevibrator electrode is formed on the sacrificial layer having theconnecting holes reaching the input electrode and the substrate,respectively, such that the edge of both end parts is disposed withinthe connecting holes. Thus, only the central part of the vibratorelectrode is disposed on the sacrificial layer in a state of the entiresurface of both ends of the vibrator electrode being disposed within theconnecting holes. Since the second conductive layer forming the vibratorelectrode can be etched selectively without affecting the firstconductive layer forming the input electrode, at the time of the patternformation of the vibrator electrode, a part of the input electrode whichpart is exposed at a bottom part of the connecting hole is not affectedby the the pattern formation of the vibrator electrode. Then, in thisstate, the sacrificial layer is selectively removed. Therefore, thevibrator electrode is formed which has a shape such that the space partis provided only under the central part and such that the entire surfaceof both end parts of the vibrator electrode is fixed to the inputelectrode and the substrate.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A to 1I are sectional process views of a manufacturing methodaccording to a first embodiment;

FIG. 2 is a plan view corresponding to FIG. 1D;

FIG. 3 is a plan view corresponding to FIG. 1G;

FIG. 4 is a plan view corresponding to FIG. 1I;

FIG. 5 is a plan view of an example of another structure of the firstembodiment;

FIGS. 6A to 6G are sectional process views of a manufacturing methodaccording to a second embodiment;

FIG. 7 is a plan view corresponding to FIG. 6D;

FIG. 8 is a plan view corresponding to FIG. 6E;

FIG. 9 is a plan view corresponding to FIG. 6G;

FIG. 10 is a plan view of an example of another structure of the secondembodiment;

FIG. 11 is a diagram showing a structure of a conventional micromachine(micro-vibrator);

FIGS. 12A to 12C are sectional process views of a conventionalmanufacturing method; and

FIG. 13 is a graph of assistance in explaining a problem of theconventional micromachine.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

Embodiments of the present invention will hereinafter be described indetail with reference to the drawings. In each of the embodiments,description will first be made of a manufacturing method, and thendescription will be made of a structure of a micromachine obtained bythe manufacturing method.

<First Embodiment>

FIGS. 1A to 1I are sectional process views of a manufacturing methodaccording to a first embodiment. FIGS. 2 to 4 are plan views ofassistance in explaining the manufacturing method according to the firstembodiment. In the following, the method of manufacturing a micromachineaccording to the first embodiment will be described on the basis ofFIGS. 1A to 1I, referring to FIGS. 2 to 4. Incidentally, FIGS. 1A to 1Icorrespond to a section A-A in the plan views of FIGS. 2 to 4.

First, as shown in FIG. 1A, a substrate 4 is formed by covering asemiconductor substrate 1 such as single-crystal silicon or the likewith an insulating layer 3. A top surface of the insulating layer 3 isformed by a material having an etching resistance to etching removal ofa sacrificial layer (silicon oxide) which removal is to be subsequentlyperformed. Accordingly, the insulating layer 3 is for example formed bylaminating a silicon oxide film 3 a for relieving stress between theinsulating layer 3 and the semiconductor substrate 1 and a siliconnitride film 3 b having the above-mentioned etching resistance in thisorder, with the silicon oxide film 3 a intermediate between the siliconnitride film 3 b and the semiconductor substrate 1.

Next, as shown in FIG. 1B, an output electrode 7 a, an input electrode 7b, and a support electrode 7 c are formed by patterning a firstconductive layer on the substrate 4. The first conductive layer formingthese electrodes 7 a to 7 c is a silicon layer such as polysiliconcontaining phosphorus (P), for example. The electrodes 7 a to 7 c arearranged on the substrate 4 such that the output electrode 7 a isinterposed between the input electrode 7 b and the support electrode 7c.

Then, as shown in FIG. 1C, a surface of the substrate 4 exposed from theelectrodes 7 a to 7 c is covered with a silicon oxide film 9. At thistime, for example, the silicon oxide film 9 is formed on only thesurface of the substrate 4 by forming the silicon oxide film on thesilicon nitride film 3 b so as to cover the electrodes 7 a to 7 c, andgrinding the silicon oxide film 9 until the electrodes 7 a to 7 c areexposed.

Next, as shown in FIG. 1D, a protective layer 11 of an insulativematerial having an etching resistance to etching removal of asacrificial layer which removal is to be subsequently performed isformed into a pattern on the substrate 4 with the input electrode 7 band the support electrode 7 c interposed between the substrate 4 and theprotective layer 11. At this time, when a sacrificial layer is formed bysilicon oxide, for example, the protective layer 11 is formed by siliconnitride (see FIG. 2).

Incidentally, the protective layer 11 is formed by etching a siliconnitride film formed over the substrate 4 using a resist pattern (notshown) as a mask, for example. At the time of this etching, the siliconoxide film 9 protects the silicon nitride film 3 b on the surface of thesubstrate 4. Thus, when the silicon nitride film 3 b has a sufficientfilm thickness for the etching to form the protective layer 11, it isnot necessary to form the silicon oxide film 9 in the previous process.When the silicon oxide film 9 is not formed, a protective layer 11 a maybe formed so as to extend from the surface of the input electrode 7 band the support electrode 7 c onto the surface of the substrate 4, asshown by a dash-double-dot line in FIG. 2. Also when the surface of thesubstrate 4 is formed of a material having a resistance to patternetching of a protective layer forming material, a similar protectivelayer 11 a indicated by the dash-double-dot line may be formed.

Thereafter, as shown in FIG. 1E, a sacrificial layer 13 is laid over theinsulating layer 3 in a state of only the protective layer 11 beingexposed. The sacrificial layer 13 is formed of a material removed byetching selectively without affecting the surface layer (the siliconnitride film 3 b in this case) of the substrate 4, the protective layer(silicon nitride in this case) 11, and the electrodes (polysilicon inthis case) 7 a to 7 c. Such a sacrificial layer 13 is formed by making asacrificial layer film in a state of covering the electrodes 7 a to 7 c,and grinding the sacrificial layer film until the protective layer 11 isexposed.

Next, as shown in FIG. 1F, a connecting hole 11 b reaching the inputelectrode 7 b and a connecting hole 11 c reaching the substrate 4 viathe support electrode 7 c are formed in the protective layer 11.

Thereafter, as shown in FIG. 1G and FIG. 3, a band-shaped vibratorelectrode 15 connected to the input electrode 7 b and the supportelectrode 7 c via the connecting holes 11 b and 11 c and crossing overthe output electrode 7 a is formed. This vibrator electrode 15 is formedby pattern etching of a second conductive layer (for example apolysilicon film) formed on the sacrificial layer 13 including theinside of the connecting holes 11 b and 11 c. At this time, the patternetching is performed such that both end parts of the vibrator electrode15 completely cover the inside of the connecting holes 11 b and 11 c, anedge of each of the end parts is situated on the protective layer 11,and a central part of the vibrator electrode 15 crosses over the outputelectrode 7 a.

Thereafter, as shown in FIG. 1H, the sacrificial layer 13 is partiallyremoved so as to expose a part for forming wiring connected to the inputelectrode 7 b in a state of the sacrificial layer 13 being left underthe vibrator electrode 15. In this case, a resist pattern (not shown)having such a shape as to cover at least the vibrator electrode 15 andthe periphery thereof and expose the part for forming wiring connectedto the input electrode 7 b is formed over the substrate 4. Then, usingthe resist pattern as a mask, the sacrificial layer 13 (silicon oxide)13 is selectively removed by etching without affecting the protectivelayer (silicon nitride) 11, the electrodes (polysilicon) 7 a to 7 c and15, and the surface layer (the silicon nitride film 3 a) of thesubstrate 4. Thereby the sacrificial layer 13 in the wiring forming partis partially removed with the sacrificial layer 13 left between thevibrator electrode 15 and the output electrode 7 a. Then, the resistpattern is removed.

Next, wiring 17 is formed in a state of being connected to an exposedsurface of the input electrode 7 b. In forming the wiring 17, a seedlayer of gold (Au) is formed over the entire surface of the substrate 4,and then a resist pattern (not shown) that exposes the wiring formingpart and covers the other parts is formed. Next, the wiring 17 is formedby growing a plating layer on the seed layer within an opening of theresist pattern by a plating method. After the wiring 17 is formed, theresist pattern is removed, and the entire surface is etched to removethe seed layer.

Thereafter, the sacrificial layer 13 is removed by etching selectivelywithout affecting the protective layer 11, the electrodes 7 a to 7 c and15, and the surface layer of the substrate 4. At this time, thesacrificial layer 13 formed by silicon oxide under the vibratorelectrode 15 is surely removed by wet etching using buffered HF. Therebya space part (gap) A is formed under the vibrator electrode 15 as shownin FIG. 1I.

As described above, as shown in FIG. 1I and FIG. 4, a micromachine 20 isobtained which has the band-shaped vibrator electrode 15 formed bylaying a beam (vibrating part) 16 over the output electrode 7 a with thespace part A interposed between the output electrode 7 a and thevibrator electrode 15 in a state in which both end parts of the vibratorelectrode 15 are supported on the input electrode 7 b and the substrate4 with the support electrode 7 c interposed between the substrate 4 andthe vibrator electrode 15.

As described with reference to FIG. 1G and FIG. 3, in particular, theabove-described manufacturing method according to the first embodimentforms the pattern of the vibrator electrode 15 so as to cover theconnecting holes 11 b and 11 c and dispose the edges of both end partsof the vibrator electrode 15 on the protective layer 11 in a state ofthe sacrificial layer 13 being formed on the substrate 4 so as to exposethe protective layer 11 having the connecting holes 11 b and 11 c formedtherein. Thus, the vibrator electrode 15 has the central part thereofdisposed on the sacrificial layer 13 in a state of the entire surface ofboth ends of the vibrator electrode 15 being disposed on the protectivelayer 11 and the connecting holes 11 b and 11 c.

Then, in this state, the sacrificial layer 13 is removed selectivelywithout affecting the protective layer 11, as described with referenceto FIG. 1I and FIG. 4. Therefore, the vibrator electrode 15 can beobtained which has a shape such that the space part A is provided onlyunder the central beam (vibrating part) 16 and such that without theedge of both end parts of the vibrator electrode 15 being extendedbeyond the surface of the protective layer 11, the entire surface fromthe edge of the end parts to the beam (vibrating part) 16 is fixed tothe input electrode 7 and the support electrode 7 c via the protectivelayer 11 and the connecting holes 11 b and 11 c.

In the micromachine 20 having the vibrator electrode 15 of such a shape,when the vibrator electrode 15 is vibrated by applying a voltage of apredetermined frequency via the input electrode 7 b, only the beam(vibrating part) 16 is involved in vibration, and vibrates. Thus, anatural frequency of the vibration is closer to the theoretical valuesatisfying the above-described Equation (1) (a value inverselyproportional to a square of length L of the vibrating part), making iteasy to achieve higher frequency by microfabrication. As a result, ahigh frequency filter having a high Q value and a higher frequency bandcan be realized.

Incidentally, when the protective layer 11 a is provided so as to extendfrom the surface of the input electrode 7 b and the support electrode 7c onto the surface of the substrate 4, as described with reference toFIG. 2, the connecting holes 11 b and 11 c formed in the protectivelayer 11 a may also have such a shape as to extend from the surface ofthe input electrode 7 b and the support electrode 7 c onto the surfaceof the substrate 4, as shown in FIG. 5. Also in this case, in forming avibrator electrode 15 a, pattern etching is performed such that both endparts of the vibrator electrode 15 a completely cover the inside of theconnecting holes 11 b and 11 c, an edge of each of the end parts issituated on the protective layer 11 a, and a central part of thevibrator electrode 15 a crosses over the output electrode 7 a. Thereby,the edge of both end parts of the vibrator electrode 15 a is notextended beyond the surface of the protective layer 11 a, and the entiresurface from the edge of the end parts to a beam (vibrating part) 16 ais fixed to the input electrode 7 and the support electrode 7 c via theprotective layer 11 a and the connecting holes 11 b and 11 c.

A micromachine 20 a having the thus formed vibrator electrode 15 a makesit possible to set line width of the vibrator electrode 15′independently of line width of the input electrode 7 b. Incidentally,the vibrator electrode 15 a in the micromachine 20 a having thestructure as shown in FIG. 5 may be formed with a constant line width.In addition, since the end parts can be set sufficiently wider than thebeam (vibrating part) 16 a, the beam (vibrating part) 16 a can besupported securely, and thus high frequency vibration closer to thetheoretical value can be achieved.

<Second Embodiment>

FIGS. 6A to 6G are sectional process views of a manufacturing methodaccording to a second embodiment. FIGS. 7 to 9 are plan views ofassistance in explaining the manufacturing method according to thesecond embodiment. In the following, the method of manufacturing amicromachine according to the first embodiment will be described on thebasis of FIGS. 6A to 6G, referring to FIGS. 7 to 9. Incidentally, FIGS.6A to 6G correspond to a section A-A in the plan views of FIGS. 7 to 9.

First, in FIG. 6A, a process is performed in the same manner asdescribed with reference to FIG. 1A in the first embodiment to form asubstrate 4 by covering a surface of a semiconductor substrate 1 such assingle-crystal silicon or the like with an insulating layer 3 formed bylaminating a silicon nitride film 3 b on a silicon oxide film 3 a.

Next, as shown in FIG. 6B, an output electrode 7 a 1, an input electrode7 b 1, and a support electrode 7 c 1 are formed by patterning a firstconductive layer on the substrate 4. The second embodiment ischaracterized in that a material having an etching resistance at thetime of pattern formation of a vibrator electrode to be formedsubsequently is used as the first conductive layer forming theelectrodes 7 a 1 to 7 c 1. Thus, when the vibrator electrode is to beformed by a silicon layer such as polysilicon, for example, theelectrodes 7 a 1 to 7 c 1 are formed by using a conductive materialhaving an etching resistance to silicon etching, for example titaniumand a titanium alloy, tungsten and a tungsten alloy, polysiliconcontaining boron (B), diamond like carbon (DLC), or diamond containingboron (B) or nitrogen (N). Incidentally, the electrodes 7 a 1 to 7 c 1are arranged in the same manner as the electrodes 7 a to 7 c of thefirst embodiment.

Then, as shown in FIG. 6C, a sacrificial layer 13 is laid over thesubstrate 4 in a state of covering the electrodes 7 a 1 to 7 c 1. Thesacrificial layer 13 is formed of a material (for example silicon oxide)removed by etching selectively without affecting the surface layer (thesilicon nitride film 3 a in this case) of the substrate 4 and theelectrodes 7 a 1 to 7 c 1.

Next, as shown in FIGS. 6D and 7, a connecting hole 13 b reaching theinput electrode 7 b 1 and a connecting hole 13 c reaching the surface ofthe substrate 4 via the support electrode 7 c 1 are formed in thesacrificial layer 13. These connecting holes 13 b and 13 c may be formedwithin areas of surfaces of the input electrode 7 b 1 and the supportelectrode 7 c 1, or may be provided as connecting holes 13 b 1 and 13 c1 extending from the surfaces of the input electrode 7 b 1 and thesupport electrode 7 c 1 onto the surface of the substrate 4, as shown bya dash-double-dot line in FIG. 7.

Thereafter, as shown in FIG. 6E and FIG. 8, a band-shaped vibratorelectrode 15 connected to the input electrode 7 b 1 and the supportelectrode 7 c 1 via the connecting holes 13 b and 13 c and crossing overthe output electrode 7 a 1 is formed. This vibrator electrode 15 isformed by making a second conductive layer (for example a polysiliconfilm) on the sacrificial layer 13 including the inside of the connectingholes 13 b and 13 c, the second conductive layer being able to be etchedwithout affecting the output electrode 7 a 1, the input electrode 7 b 1,and the support electrode 7 c 1, and performing selective patternetching of the second conductive layer.

The vibrator electrode 15 is formed in a pattern such that both endparts of the vibrator electrode 15 do not extend from within theconnecting holes 13 b and 13 c. Therefore, in the case of the connectingholes 13 b 1 and 13 c 1 having a shape extending from the surface of theinput electrode 7 b 1 and the support electrode 7 c 1 onto the surfaceof the substrate 4, both end parts of the vibrator electrode 15 may alsobe formed so as to extend onto the surface of the substrate 4.

Thereafter, as shown in FIG. 6F, the sacrificial layer 13 is removedpartially in a wiring forming part with the sacrificial layer 13 beingleft in a space under the vibrator electrode 15, and then wiring 17connected to the input electrode 7 b 1 is formed. This process isperformed in the same manner as described with reference to FIG. 1H inthe first embodiment.

Thereafter, the sacrificial layer 13 is removed by etching selectivelywithout affecting the electrodes 7 a 1 to 7 c 1 and 15, the surfacelayer of the substrate 4, and the wiring 17. Thereby, as shown in FIG.6G and FIG. 9, a space part (gap) A is formed under the vibratorelectrode 15. This process is performed in the same manner as describedwith reference to FIG. 1I in the first embodiment.

As described above, a micromachine 21 is obtained which has theband-shaped vibrator electrode 15 formed by laying a beam (vibratingpart) 16 over the output electrode 7 a 1 with the space part Ainterposed between the output electrode 7 a 1 and the vibrator electrode15 in a state in which both end parts of the vibrator electrode 15 aresupported on the input electrode 7 b 1 and the substrate 4 with thesupport electrode 7 c 1 interposed between the substrate 4 and thevibrator electrode 15.

As described with reference to FIG. 6E and FIG. 8, in particular, theabove-described manufacturing method according to the second embodimentforms the pattern of the vibrator electrode 15 such that an edge of bothend parts of the vibrator electrode 15 is disposed within the connectingholes 13 b and 13 c provided in the sacrificial layer 13. At this time,since the second conductive layer forming the vibrator electrode 15 canbe etched selectively without affecting the first conductive layerforming the input electrode 7 b 1 and the support electrode 7 c 1, thepattern of the vibrator electrode 15 can be formed without affecting theinput electrode 7 b 1 and the support electrode 7 c 1 exposed at abottom part of the connecting holes 13 b and 13 c at the time of formingthe pattern of the vibrator electrode. As a result of the patternformation, the vibrator electrode 15 has only a central part thereofdisposed on the sacrificial layer 13 with the entire surface of bothends of the vibrator electrode 15 being disposed within the connectingholes 13 b and 13 c.

Then, in this state, the sacrificial layer 13 is removed selectively, asdescribed with reference to FIG. 6G. Therefore, the vibrator electrode15 can be obtained which has a shape such that the space part A isprovided only under the central beam (vibrating part) 16 and such thatthe entire surface of both end parts of the vibrator electrode 15 isfixed to the input electrode 7 b 1 and the support electrode 7 c 1 onthe substrate 4.

Also in the micromachine 21 having the vibrator electrode 15 of such ashape, as in the micromachines 20 and 20 a according to the firstembodiment, when the vibrator electrode 15 is vibrated by applying avoltage of a predetermined frequency via the input electrode 7 b, onlythe beam (vibrating part) is involved in vibration, and vibrates. Thus,a natural frequency of the vibration is closer to the theoretical value(the value inversely proportional to the square of length L of thevibrating part), making it easy to achieve higher frequency bymicrofabrication. As a result, a high frequency filter having a high Qvalue and a higher frequency band can be realized.

Incidentally, when the connecting holes 13 b 1 and 13 c 1 are providedso as to extend from the surface of the input electrode 7 b and thesupport electrode 7 c onto the surface of the substrate 4 as describedwith reference to FIG. 7, both end parts of a vibrator electrode 15 acan also be formed so as to extend onto the surface of the substrate 4,as shown in FIG. 10. It is therefore possible to set line width of thevibrator electrode 15 a independently of line width of the inputelectrode 7 b 1. Such a vibrator electrode 15 a may be formed with aconstant line width or may be formed with only end parts having agreater line width. In addition, since the end parts can be setsufficiently wider than the beam (vibrating part) 16 a, the beam(vibrating part) 16 a can be securely supported. Thus a micromachine 21a that can achieve high frequency vibration closer to the theoreticalvalue can be obtained.

When the support electrode 7 c 1 is not formed in the above-describedsecond embodiment, the connecting hole 13 c is formed so as to reach thesubstrate 4 in the process described with reference to FIG. 6D. Therebya micromachine that can provide similar effects is obtained.

INDUSTRIAL APPLICABILITY

As described above, in accordance with a micromachine and a method formanufacturing the same according to the present invention, a vibratorelectrode is formed such that a space part is provided only under a beam(vibrating part) and the entire surface of both end parts supporting thebeam is fixed to an input electrode and a base such as a substrate orthe like. Thus, when the vibrator electrode is vibrated by applying avoltage of a predetermined frequency via the input electrode, only thebeam (vibrating part) is involved in vibration, and therefore a naturalfrequency of the vibration closer to the theoretical value can beobtained. It is thereby possible to facilitate achievement of higherfrequency by microfabrication of the vibrator electrode, and thusrealize a high frequency filter having a high Q value and a higherfrequency band.

1. A micromachine comprising: a substrate; a first electrode, a secondelectrode, and a support electrode disposed on said substrate; one ormore protective films disposed on said first electrode and said supportelectrode; and a band-shaped vibrator electrode comprising (a) avibrating part overlaying said second electrode, the vibrating partbeing spaced apart from the second electrode with a gap therebetween,and (b) end parts secured to said first electrode and said supportelectrode, a portion of each end part overlying one of the protectivefilms.
 2. A micromachine as claimed in claim 1, wherein, said vibratorelectrode is formed of a material capable of being etched selectivelywithout affecting a material of said first electrode.
 3. A micromachineas claimed in claim 1, wherein, a width of the end part of said vibratorelectrode which is fixed to said first electrode is greater than thewidth of said first electrode.
 4. A micromachine as set forth in claim1, wherein said first electrode is an input electrode and said secondelectrode is an output electrode.